Method and apparatus for manufacturing color picture tubes

ABSTRACT

In a method of manufacturing a color picture tube wherein the phosphor coated on the inner surface of the panel of the tube is exposed to the light emanated from a source of light and transmitting through a correction lens having a discontinuous surface, the phosphor is exposed to the light while continuously changing the relative positions of the panel, the source of light and the correction lens thereby uniformly exposing the phosphor.

United States Patent 1191 Takemoto et al. 1 Jan. 8, 1974 METHOD AND APPARATUS FOR 3,559,546 2/1971 McKee 95/1 MANUFACTURING COLOR PICTURE TUBES Primary ExaminerJohn M. Horan :Tk Tk t-E hYamazaki, [75] Inventors 25 2 2323;, ti d a" Attorney-Charles E. Pfund. Esq.. (.hlmck. Thompof Mobara, Japan I Pfund I [73] Assignee: Hitachi, Ltd., Tokyo, Japan [22] Filed: Mar. 2, 1972 7- ABSTRACT [21] Appl. No.: 231,312

In a method of manufacturing a color picture tube [30] For i n A li ti n P i it D t wherein the phosphor coated on the inner surface of Mar '5 1971 Japan 46/11275 the Pamel 9 the tube is eXPOSed to the light emanated from a source of-light and transmitting through acor- 52 us. c1 95/1'R Teeth)" lens having a discontinuous surface, the P 511 1m. (:1. .L G03b 27/02 Phhr is exposed to the light While Continuously Chang- [58] Field of Search 95/1 ing the relative 0f the P the some of v light and the correction lens thereby uniformly expos- [56] References Cited mg the phosphor UNITED STATES PATENTS 3,21 1,067 10/1965 Kaplan 95/1 14 Claims, 6 Drawing Figures PATENIEDJAH 81974 3783,7554

sum 10? 3 Pmgmgnm 8 1914 3783,75 1

sum 2 or 3 PATENTEDJAH 81974 v $783,754

SHEET 30F 3 METHOD AND APPARATUS FOR MANUFACTURING COLOUR PICTURE TUBES BACKGROUND OF THE INVENTION This invention relates to a method and apparatus for manufacturing colour picture tube and more particularly to a method and apparatus for manufacturing fluorescent screens thereof.

Generally, the fluorescent screen of a colour picture tube is manufactured by applying in a regular pattern a plurality of trios and phosphor dots of three colours on the inner surface of the face plate or the panel of the tube by photographic technique.

When forming the phosphor dots by photographic technique a correction lens having an extremely complicated curved surface is used for the purpose of causing the locus of the exposure light emanated from a source of light to approximate the locus of the electron beam prevailing in the completed tube.

As most of the conventional correction lenses have a continuously curved surface, with such lenses it has been impossible to perfectly align the locus of the exposure light with that of the electron beam. For this reason, it has been impossible to perfectly align the phosphor dots and the electron beam spots over the entire inner surface of the panel. As a consequence, the colour picture tube having a fluorescent screen formed with such a correction lens having a continuously curved surface has an inherent drawback of accompanying the problem of colour shading and hence poor quality of the reproduced picture.

. To solve this problem, an improved correction lens has been proposed. FIG. 1 of the accompanying drawing shows a plane view of such a correction lens, FIG. 2 the cross-section thereof and FIG. 3 a panel 4 having a fluorescent screen formed with the correction lens shown in FIGS. 1 and 2 and viewed from the exterior of the tube.

As shown by FIG. 1, the upper or effective surface of the correction lens is divided into a plurality of small rectangular regions 2 partitioned by grid shaped boundary lines 3. As shown in FIG. 2, the surface of each region is a flat or slightly curved surface inclined to the bottom surface of the lens 1 so that the upper or effective surface of the lens is a discontinuous surface and the boundary lines 3 or the portions interconnecting adjacent rectangular regions form steep vertical side surfaces. Since the flat or slightly curved surfaces and the vertical side surfaces manifest different transmission characteristics to the light transmitting through the correction lens, the fluorescent screen formed on the panel 4 with this correction lens has portions 5 corresponding to flat regions 2 and grid shaped portions 6 corresponding to boundary lines 3, as shown in FIG. 3, portions 5 and 6 having been exposed to light of different intensities. Such grid shapedpattem caused by nonuniform exposure is seen from outside of the tube whether it is operating .or not, thus degrading thequality of the reproduced picture.

SUMMARY OF THE INVENTION It is therefore an object of this invention to provide a new and improved method and apparatus capable of producing a colour picture tube having a uniformly exposed fluorescent screen by using a correction lens having discontinuous surfaces.

According to one aspect of this invention, there is provided a method of manufacturing a colour picture tube wherein the phosphor coated on the inner surface of the panel of the tube is exposed to the light emanated from a source of light and transmitting through a correction lens having a discontinuous surface, characterized in that the phosphor is exposed to the light while continuously changing the relative positions of the panel, the source of light and the correction lens thereby uniformly exposing the phosphor.

According to another feature of the invention. there is provided apparatus for manufacturing a colour picture tube comprising a source of light and a correction lens having discontinuous surfaces and disposed between the panel of the tube and the source of light whereby the phosphor coated on the inner surface of the panel is exposed to the light from the source and transmitting through the correction lens to form a fluorescent screen, characterized in that there is provided means for continuously changing the relative positions of the panel, the correction lens and the source of light while the phosphor is exposed, thereby assuring uniform exposure.

Since the purpose of providing the means for continuously changing the relative positions is to eliminate the adverse effect caused by the boundary lines between the divided regions of the correction lens, such means may be associated with any one of the panel, the source of light and the correction lens. Where the surface of the correction lens is divided into a plurality of rectangular regions as above described said means may comprise a first and a second drive means which are operated simultaneously to continuously move the correction lens along a diagonal of one rectangular region.

BRIEF DESCRIPTION OF THE DRAWINGS Further objects and advantages of the invention can be more fully understood from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 shows a plane view of a correction lens having a discontinuous surface and utilized to carry out the invention;

FIG. 2 is a sectional view of the correction lens shown in FIG. ll, taken along a line II ll;

FIG. 3 is a diagrammatic representation of a'panel of a colour picture tube having a fluorescent screen formed by using the correction lens shown in FIGS. 1 and 2;

FIG. 4 shows a diagrammatic longitudinal section of the exposure device utilized to carry out the invention;

FIG. 5 is a diagram to explain the method of manufacturing a fluorescent screen in accordance with this invention; and I FIG. 6 is a plan view showing the detail of the means for shifting the correction lens, light source or panel.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the accompanying drawing, one example of an exposure device utilized to form the fluorescent screen of a colour picture tube in accordance with the method of this invention is shown in FIG. 4. The exposure device 11 shown therein comprises a source of light 12, a correction lens 13 which is identical to that shown in FIGS. 1 and 2 and is used for the purpose of causing the locus of the light emanatedfrom the source of light 12 to approximate the locus of electron beam prevailing in the completed colour picture tube, and means 14 for shifting the position of the correction lens 13. The panel 16 provided with the shadow mask 15 of the colour picture tube is mounted on the upper end of the exposure device 11. According to this invention, the phosphor applied onto the inner surface of the panel 16 is exposed to the light emanated from source 12 and transmitting through the correction lens 13 while it is being continuously moved by the shifting means 14. More particularly, the correction lens 13 is continuously moved along a diagonal 19 or 20 passing through the center 20 of a square 17 representing one region 2 of the correction lens 13. When the fluorescent screen is exposed to the light while continuously shifting the correction lens in this manner, the cross strips 6 caused by the grid shaped boundary lines 6 will be evenly distributed over the entire surface of the phosphor thereby assuring uniform exposure of the entire area of the fluorescent screen.

As diagrammatically shown in FIG. 6, means 14 for shifting the correction lens 13 (or light source 12 or panel 16 comprises drive means 21 for driving the correction lens 13 in the direction of Y, a base plate 22 on which is secured the driving means 21 and a drive means 23 for driving the base plate 22 in the direction of X.

Thus, when drive means 21 is operated correction lens 13 is moved in the direction of Y whereas when drive means 23 is operated correction lens 13 is moved in the direction of X together with drive means 21. Accordingly, when drive means 21 and 23 are operated simultaneously at a speed ratio corresponding to the ratio of the longitudinal to the transversal dimension of one region of the correction lens 13, the correction lens will be moved along a diagonal 19 or 20.

Although in the above described embodiment, during exposure of the phosphor the correction lens is moved continuously in the direction of a diagonal of one of the divided regions, the direction of movement of the correction lens is not limited to this particular direction but the correction lens may be moved in any direction that can assure uniform exposure of the fluorescent screen or can eliminate uneven exposure due to the boundary lines between the divided regions.

Further, it should be understood that the same object can also be accomplished by changing the relative positions of the panel of the colour picture tube, the correction lens and the source of light. Thus, the shifting mans 14 shown in FIG. 6 may be provided for either the source of light 12 or the panel 16. It should also be understood that, in addition to the shadow mask type colour picture tube described above, the invention can also be applied to a colour picture tube having a fluorescent screen in which phosphors of three colours are applied in the form of parallel stripes.

As above described, according to the method and apparatus of this invention there is provided a colour picture tube having a uniformly exposed fluorescent screen thereby improving the quality of the reproduced picture.

What is claimed is:

1. In a method of manufacturing a colour picture tube wherein the phosphor coated on the inner surface of the panel of said tube is exposed to the light emanated from a source of light and transmitting through a correction lens having a plurality of discontinuous elemental lens surfaces contiguously joined bylight diffusing boundaries which define the perimeters of said surfaces, the improvement which comprises the step of exposing said phosphor while continuously changing the relative positions of said panel, said source of light and said correction lens by moving along a transverse dimension of the elemental area of said lens surfaces and moving an amount to extend over the elemental area of said lens surfaces which distributes the image of said boundaries on said inner surface for substantially uniformly exposing said phosphor.

2. The method according to claim I wherein said panel and said source of light are held stationary and said correction lens is moved continuously.

3. The method according to claim 2 wherein said correction lens has a surface which is divided into a plurality of discontinuous rectangular regions and said correction lens is moved along a diagonal of one rectangular region.

4. The methodaccording to claim 1 wherein said panel and said correction lens is held stationary and said source of light is moved continuously.

5. The method according to claim 1 wherein said correction lens and said source'of light are held stationary and said panel is moved continuously.

6. In apparatus for manufacturing a colour picture tube comprising a source of light, and a correction lens having a plurality of discontinuous elemental lens surfaces contiguously joined by light diffusing boundaries which define the perimeters of said surfaces and disposed between the panel of said tube and said source of light whereby the phosphor coated on the inner surface of said panel is exposed to the light from said source and transmitted through said correction lens to form a fluorescent screen, the improvement which comprises means continuously changing the relative positions of said panel, said correction lens and said source of light by an amount and direction which distributes the image of said boundaries on said inner surface while said phosphor is exposed for assuring substantially uniform exposure.

7. The apparatus according to claim 6 wherein said continuously changing means continuously moves at least one of said panel, said correction lens and said source of light, thereby causing continuous changing of the relative positions of said panel, said correction lens and said source of light. I

8. The apparatus according to claim 7 wherein said continuously changing means comprises a drive means for moving said correction lens.

9. The apparatus according to claim 8 wherein said drive means for moving said correction lens comprises a first drive means for moving said correction lens in a first direction, a base plate supporting said first drive means, and a second means for driving said base plate in a second direction.

10. The apparatus according to claim 7 wherein said continuously changing means comprises a drive means for moving said panel.

1 1. The apparatus according to claim 10 wherein said drive means for moving said panel comprises a first drive means for moving said panel in a first direction, a base plate supporting said first drive means, and a second means for driving said base plate in a second direction.

in second direction.

14. The apparatus according to claim 9 wherein said correction lens has surfaces divided into a plurality of discontinuous rectangular regions and said first and second drive means are operated simultaneously for moving said correction lens along a diagonal of one rectangular region.

v UNl'l'l-ll) S'IA'II'ZS IA'I'I'PN'I" ()FFHII-l GER/l! FIG/YUP) ()F (1) ii H HUI. I )N Patent; :10. 3,793,754 Dated vJanuary 8, 1974 Takeo Takemoto, EiicTli Yamazaki, KoicFhi Maruyama; Toshio Ueda It. is cert'l [ii- 1 that error appears in Um nhovu-im-nti fic-d pznn-nt; and that said Letters la Lent. are hereby corrvcu-d as; shown he] ow:

In"[75] Inventorsz" correct the spelling of -the name "Eiich" to read Eiichi Column 1, line 34, change "plane" to plan Colur nn 2,' line 42;, change "plane" to plan Column 3, line l'7 change "strips" to stripes Column 3,- linef23, af ter "panel 16" 1 I insert a parenthesis sign Column 3, line 49, "mans" should be means Signed and sealed this 30th day of July l974.

(SEAL) Attest:

MCCOY M. GIBSON, JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents Takeo Takemoto, Eiichi Yamazaki, Koichi Maruyama; Toshio 'Ueda It. is cm'ti [ii-d that error appears in the. nhovc-MvnLi Tic-d pun-m; and that said Letters: Patent. are hereby corrvcu-d as shown below:

In"[75] Inventorsz" correct the spelling of the name "Eiich" to read Eiichi Column 1, line 34, change "plane" to plan Column 2, 1111542, change "plane" to plan Column 3, line l7, change "strips" to stripes Column 3, line '23, after "panel 16" M V i I insert a parenthesis sign Column 3, line 49, "mans" should be means Signed and sealed this 30th .day of Julyv 1974.,

(SEAL) Attest:

McCOY M. GIBSON', "JR. C. MARSHALL DANN Attesting Officer Y Commissioner of Patents 

1. In a method of manufacturing a colour picture tube wherein the phosphor coated on the inner surface of the panel of said tube is exposed to the light emanated from a source of light and transmitting through a correction lens having a plurality of discontinuous elemental lens surfaces contiguously joined by light diffusing boundaries which define the perimeters of said surfaces, the improvement which comprises the step of exposing said phosphor while continuously changing the relative positions of said panel, said source of light and said correction lens by moving along a transverse dimension of the elemental area of said lens surfaces and moving an amount to extend over the elemental area of said lens surfaces which distributes the image of said boundaries on said inner surface for substantially uniformly exposing said phosphor.
 2. The method according to claim 1 wherein said panel and said source of light are held stationary and said correction lens is moved continuously.
 3. The method according to claim 2 wherein said correction lens has a surface which is divided into a plurality of discontinuous rectangular regions and said correction lens is moved along a diagonal of one rectangular region.
 4. The method according to claim 1 wherein said panel and said correction lens is held stationary and said source of light is moved continuously.
 5. The method according to claim 1 wherein said correction lens and said source of light are held stationary and said panel is moved continuously.
 6. In apparatus for manufacturing a colour picture tube comprising a source of light, and a correction lens having a plurality of discontinuous elemental lens surfaces contiguously joined by light diffusing boundaries which define the perimeters of said surfaces and disposed between the panel of said tube and said source of light whereby the phosphor coated on the inner surface of said panel is exposed to the light from said source and transmitted through said correction lens to form a fluorescent screen, the improvement which comprises means continuously changing the relative positions of said panel, said correction lens and said source of light by an amount and direction which distributes the image of said boundaries on said inner surface while said phosphor is exposed for assuring substantially uniform exposure.
 7. The apparatus according to claim 6 wherein said continuously changing means continuously moves at least one of said panel, said correction lens and said source of light, thereby causing continuous changing of the relative positions of said panel, said correction lens and said source of light.
 8. The apparatus according to claim 7 wherein said continuously changing means comprises a drive means for moving said correction lens.
 9. The apparatus according to claim 8 wherein said drive means for moving said correction lens comprises a first drive means for moving said correction lens in a first direction, a base plate supporting said first drive means, and a second means for driving said base plate in a second direction.
 10. The apparatus according to claim 7 wherein said continuously changing means comprises a drive means for moving said panel.
 11. The apparatus according to claim 10 wherein said drive means for moving said panel comprises a first drive means for moving said panel in a first direction, a base plate supporting said first drive means, and a second means for driving said base plate in a second direction.
 12. The apparatus according to claim 7 wherein said continuously changing means comprises a drive means for moving said source of light.
 13. The apparatus according to claim 12 wherein said drive means for moving said source of light comprises a first drive means for moving said source of light in a first direction, a base plate supporting said first drive means, and a second means for driving said base plate in second direction.
 14. The apparatus according to claim 9 wherein said correction lens has surfaces divided into a plurality of discontinuous rectangular regions and said first and second drive means are operated simultaneously for moving said correction lens along a diagonal of one rectangular region. 